From: gherold@teachspin.com   
      
   On Tuesday, October 23, 2018 at 4:03:05 AM UTC-4, Sebastia RodaMon wrote:   
   > El dimarts, 23 octubre de 2018 1:35:47 UTC+2, George Herold va escriure:   
   > > On Monday, October 22, 2018 at 9:44:54 AM UTC-4, George Herold wrote:   
   > > > On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:   
   > > > > Hi - I got a brand new solar cell "Eco Line ES10M36".   
   > > > >   
   > > > > In my garden, under full sun it provides 21 volts and 500 mA,   
   > > > > and under big shadow it gives 18 volts and 30 mA.   
   > > > >   
   > > > > Load is a 24 volt bulb lamp in series with the Fluke.   
   > > > >   
   > > > > As the voltage margin is small, I want to detect the intensity   
   > > > > to determine if there is sun or not.   
   > > > >   
   > > > > What electronic circuit would you recommend to do it ?   
   > > > >   
   > > > > If I place 2 resistors conected in serial,   
   > > > > the voltage drop will have the same small margin the cell has ...   
   > > > >   
   > > > > Thanks.   
   > > >   
   > > > Sounds like you have some circuit working already.   
   > > > I don't know (big) solar cells.  For little photodiodes and   
   > > > things you can either measure the open circuit voltage   
   > > > (V~log (Intensity)) or the short circuit current,   
   > > > (I~ Intensity)   
   > > >   
   > > > George h.   
   > >   
   > > If your'e getting power from it, then measure I-V   
   > > along the 'diode' curve... modulate something a little bit.   
   > >   
   > > George H.   
   > > (are solar panels at all close to 'ideal diodes'?)   
   >   
   > mr George : the solar cell is not a "working" one,   
   > but a small one (30 cm x 30 cm, max 10 W) to be used as "monitor" of sun   
   light.   
   >   
   > Anyway, of course I want to measure I/V along the diode curve.   
   >   
   > My problem is I know no circuit to do that.   
   >   
   > Thanks. Ceba.   
      
   30 cm x 30 cm is pretty big compared to things I use.   
   But still measure Voltage OC or current SC... Or along the way   
   Assuming you have a few millamps to power things you could make   
   an opamp-Fet-R current sink and measure the voltage as a function   
   of current.  10W you'd need a heat sink.  How about a smaller solar cell?   
      
   George H.   
      
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